The use of natural and synthetic materials for bone repair is known. Most of the synthetic materials share numerous advantages over natural materials (including allograft bone, autograft bone and demineralized bone matrix (“DBM”)) such as unlimited supply, elimination of disease transmission, elimination of second surgery, and the ability to be shaped into various shapes and sizes. Many synthetic bone grafts include materials that closely mimic mammalian bone, such as compositions containing calcium phosphates. Exemplary calcium phosphate compositions contain type-B carbonated hydroxyapatite [Ca5(PO4)3x(CO3)x(OH)], which is the principal mineral phase found in the mammalian body. The ultimate composition, crystal size, morphology, and structure of the body portions formed from the hydroxyapatite are determined by variations in the protein and organic content. Calcium phosphate ceramics have been fabricated and implanted in mammals in various forms including, but not limited to, shaped bodies and cements. Different stoichiometric compositions such as hydroxyapatite (“HAp”), tricalcium phosphate (“TCP”), tetracalcium phosphate (“TTCP”), and other calcium phosphate salts and minerals, have all been employed to match the adaptability, biocompatibility, structure, and strength of natural bone. The role of pore size and porosity in promoting revascularization, healing, and remodeling of bone has been recognized as a critical property for bone grafting materials. The preparation of exemplary porous calcium phosphate materials that closely resemble bone have been disclosed, for instance, in U.S. Pat. Nos. 6,383,519 and 6,521,246, incorporated herein by reference in their entirety.
Recently, in an attempt to broaden the use of bone graft materials throughout the body, pliable and injectable bone graft compositions have been fabricated. Some of these attempts have been disclosed in U.S. Pat. No. 5,324,519 to Dunn, et al.; U.S. Pat. No. 5,352,715 to Wallace et al.; U.S. Pat. No. 6,287,341 to Lee et al.; U.S. Pat. No. 6,214,368 to Lee et al.; U.S. Pat. No. 6,652,887 to Richelsoph et al.; and U.S. Pat. No. 6,288,043 to Spiro et al. However, these attempts suffer from numerous shortcomings. Some compositions are made of thermoplastic polymers as opposed to calcium phosphate. There are injectable implant compositions that teach having ceramic:collagen ratios requiring a collagen dominance. There are also compositions used as implants made of poorly crystalline apatitic calcium phosphate defined by a specific XRD spectrum and FTIR pattern. Other attempts have focused on compositions made from calcium sulfate.
Furthermore, many of these bone attempts include materials that do not optimally resorb (e.g., thermoplastic polymers, amorphous calcium phosphate, calcium sulfate dihydrate) or structures that do not have the ideal porosity and pore size distribution to promote bone formation. Other attempts require the addition of a carrier, such as hyaluronic acid or glycerol, or a plasticizer in a high percentage so that the compositions may be shaped or injected. Several also require that the mineral component particle size be smaller than 250 μm to facilitate injection.
There is a need for resorbable, porous, shapeable bone graft materials that maintain ideal osteoconductivity properties and offer convenient delivery for a variety of applications. The present invention includes optimal materials, with optimal porosities in optimal size ranges for promoting bone formation. Although generally useful, the present invention is particularly suitable in trauma and orthopaedic applications, in which the size and the shape of the defects to be repaired are irregular or variable.
It is an object of this invention to provide biocompatible graft materials with superior osteoconductive properties.
It is also an object of this invention to provide flowable graft materials for restoring defects in bone.
It is another object of this invention to provide shapeable bone graft materials that can occupy voids of varying shapes.
It is another object of this invention to provide injectable bone graft materials with improved handling properties that resorb.
It is yet another object of this invention to provide injectable bone graft materials that still retain high degrees of porosity over a broad pore size distribution to maintain superior resorption and bone ingrowth properties.
It is yet another object of the invention to provide injectable bone graft materials with fluid wicking and retention properties.
It is also an object of this invention to provide porous, pliable bone graft materials capable of delivering cells and molecules to the body.
It is also an object of this invention to provide a bone graft material capable of being mixed with other graft materials while maintaining injectability.
It is a further object of this invention to provide an injectable, resorbable bone graft material and instruments for delivery thereof.
It is a further object of this invention to provide bone grafts with delivery instruments capable of low-pressure delivery of injectable bone graft materials.
Additional objects, advantages, and novel features of this invention will become apparent to those skilled in the art upon examination of the following descriptions, figures and claims thereof, which are not intended to be limiting.